---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 10/05/21: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:20 AM - Re: Integration of Rotax 912iS (user9253) 2. 06:14 AM - Re: Re: Integration of Rotax 912iS (C&K) 3. 07:59 AM - Re: Integration of Rotax 912iS (Eric Page) 4. 10:40 AM - Re: Integration of Rotax 912iS (user9253) ________________________________ Message 1 _____________________________________ Time: 05:20:06 AM PST US Subject: AeroElectric-List: Re: Integration of Rotax 912iS From: "user9253" It looks like the relay will be energized whenever the engine is running. If the engine quits, you will turn on the backup switch. So the relay will still be energized and depleting the battery that is needed to keep the engine running. Or is my reasoning wrong? -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=503416#503416 ________________________________ Message 2 _____________________________________ Time: 06:14:19 AM PST US Subject: Re: AeroElectric-List: Re: Integration of Rotax 912iS From: C&K Figure 3.18: Wiring Powerside (optional) in the install manual shows backup power bypassing the battery contactor which seems like the preferred architecture to me. Interestingly I recently had a battery contactor go high resistance. It would run the panel and lights but instantly went open circuit when the starter was engaged. Looked like new except the internal copper parts had a black coating. Ken On 05/10/2021 8:19 AM, user9253 wrote: > > It looks like the relay will be energized whenever the engine is running. If the engine quits, you will turn on the backup switch. So the relay will still be energized and depleting the battery that is needed to keep the engine running. Or is my reasoning wrong? > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=503416#503416 > > ________________________________ Message 3 _____________________________________ Time: 07:59:06 AM PST US Subject: AeroElectric-List: Re: Integration of Rotax 912iS From: "Eric Page" user9253 wrote: > It looks like the relay will be energized whenever the engine is running. Correct. As long as the Backup Battery switch is open, the P-channel MOSFET is turned on by the pull-down resistor on its gate, allowing current to flow through the relay coil. > If the engine quits, you will turn on the backup switch. So the relay will still be energized and depleting the battery that is needed to keep the engine running. Or is my reasoning wrong? No, turning on the Backup Battery switch applies ~12V to the MOSFET gate, turning it off, which stops current flow to the relay coil. I've confirmed that there's no current path from pin X3-3 (normal power input) to pin X3-1, so there's no voltage on pin X3-1 in normal operation. HOWEVER... It turns out that pins X3-1 and X3-2 are shorted inside the Fuse Box, which makes sense given that the Backup Battery and Start Power switches do essentially the same thing. This means that closing the Start Power switch will open my relay, which is definitely not the behavior I want. Thanks for making me think this through, Joe. VERY helpful! Eric Read this topic online here: http://forums.matronics.com/viewtopic.php?p=503425#503425 ________________________________ Message 4 _____________________________________ Time: 10:40:20 AM PST US Subject: AeroElectric-List: Re: Integration of Rotax 912iS From: "user9253" There might be voltage on X3-1 when the engine is running if using EMS Ground as the reference point. That should not disable the transistor which uses airframe ground. Isolated grounds make it confusing. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=503432#503432 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.